When a patient is admitted with a localized infection and sepsis develops after admission, the localized infection is generally sequenced as the principal diagnosis, followed by the appropriate sepsis code.
The FY 2026 ICD-10-CM Official Guidelines explicitly distinguish this circumstance from cases in which both the localized infection and sepsis are present on admission. When sepsis develops only after admission, the localized infection responsible for the original hospitalization remains principal.
Therefore, pneumonia is sequenced first in this scenario.
If the patient subsequently develops acute organ dysfunction related to sepsis and the provider documents severe sepsis, additional severe-sepsis and organ-dysfunction codes are assigned as appropriate. The severe-sepsis code cannot itself serve as principal diagnosis.
This question demonstrates why CDI specialists must clarify timing. Simply seeing both “pneumonia” and “sepsis” in a discharge summary is insufficient to determine correct sequencing when the onset relationship is unclear.
The POA status of sepsis also becomes relevant because documentation indicates that it developed after inpatient admission.
CCDS Reference Topics: Sepsis; pneumonia; sequencing; timing; POA; principal diagnosis.
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